Coiled insect fumigant

ABSTRACT

Disclosed herein are mosquito coils having an enlarged outer portion for providing quick coverage of an insect control ingredient in a space that previously had none. The coil is provided with urea for greater breakage resistance and kerosene and peanut shell powder to improve igniting and burning characteristics.

This is a division of application Ser. No. 08/647,616 filed on May 13,1996, U.S. Pat. No. 5,657,574.

TECHNICAL FIELD

The present invention relates to mosquito coils and other burnableinsect control ingredient delivery devices. More particularly, itprovides breakage resistant fumigants that deliver a large burst of aninsect control ingredient when they are initially lighted, followed by alower, essentially steady state level thereafter.

BACKGROUND ART

Mosquito coils are coils of slowly burnable solid material that containan insect control ingredient such as a repellent, an insecticide, or aninsect growth regulator. When they burn, heat vaporizes (and therebydisperses) the insect control ingredient. Small amounts of smoke alsohelp to disperse the insect control ingredient.

U.S. Pat. No. 5,447,713 discloses a mosquito coil having a conventionalspiral configuration, and U.S. Pat. No. 3,754,861 teaches a mosquitocoil having a match-like ignition tip containing potassium chloride asan oxidizer (albeit the tip does not contain any insect controlingredient). Also known are solid fumigants in certain other shapes. Seee.g. U.S. Pat. No. 4,959,925.

Various compositions for such solid fumigants are known. For example,U.S. Pat. No. 4,144,318 teaches the use of allethrin, tabu powder,starches, wood powder, coco shell powder, and dye in mosquito coils, andU.S. Pat. No. 4,296,091 teaches the use of a perfume in a mosquito coil.

One drawback of prior art mosquito coils is that no provision was madeto provide quick coverage for a room or other environment thatpreviously had no insect control ingredient in it. Thus, the environmentcould not safely be used for an inconveniently long time.

Another drawback of the prior art coils is that they broke too easilyduring manufacture and handling.

A difficulty in trying to address such problems is that mosquito coilsmust be made so that they can be easily lit, yet they must burn at avery slow rate once lit so as to provide extended protection throughoutthe night. This places significant limitations on the shape andcomposition of mosquito coils.

It can be seen that a need exists for improved mosquito coils.

DISCLOSURE OF THE INVENTION

In one aspect the invention provides a burnable insect fumigant coil.The fumigant coil has a radially outward insect controlingredient-containing region that is linked to an insect controlingredient-containing inner coil. The inner coil extends radially inwardfrom the radially outward region in a spiral fashion. The radiallyoutward region has a cross-sectional area that is greater than across-sectional area of the inner coil which is immediately adjacent theradially outward region. The fumigant coil is configured and constitutedsuch that upon lighting the fumigant coil at an outer end the fumigantcoil can disperse insect control ingredient at a greater rate whenburning through a portion of the radially outward region than when itbegins burning the inner coil.

The burnable insect fumigant coil can have the radially outward regionalso linked to an ignition region. The ignition region can have asmaller cross-sectional area than the cross-sectional area of theradially outward region. The fumigant coil can also (or alternatively)contain kerosene to overcome any difficulties in lighting a coil withsuch an enlarged radially outward region.

Preferably, the fumigant coil contains urea to provide flexibility andpeanut shell powder to provide for smoother burning.

Another aspect of the present invention provides a burnable insectcontrol ingredient delivery device having an insect control ingredient,at least one burnable base material selected from the group consistingof wood powder and vegetable shell powder, and at least 0.1% urea.Preferably, the delivery device is in the shape of a coil, has at least0.05% by weight of kerosene, at least 0.05% by weight of peanut shellpowder, and 0.10% to 5.00% by weight of urea.

A further aspect of the present invention is a method of fumigating anenvironment. One places the above burnable insect fumigants coil in anenvironment and ignites it. The environment might, for example, be abedroom of a building. It might also be the inside of a tent or anunenclosed environment.

The objects of the present invention therefore include providing amosquito coil:

(a) having an enlarged outer portion to provide quick coverage with arepellent or another insect control ingredient;

(b) having a second coiled inner portion which has a substantiallyconstant, lesser cross-sectional area so that fumigant waste isminimized once the room already has an adequate base concentration offumigant dispersed in the air; and

(c) which contains urea to provide flexibility.

The invention can also provide coils made of inexpensive materials,which can be inexpensively manufactured, and which do not containenvironmentally unacceptable materials.

These and still other objects and advantages of the present invention(e.g., methods for using the coils) will be apparent from thedescription which follows. The following description is merely of thepreferred embodiments. Thus, the claims should be looked to in order tounderstand the full scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a preferred embodiment of the presentinvention;

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 1;

FIG. 4 is a top plan view of a second embodiment of the presentinvention; and

FIG. 5 is a top plan view of a third embodiment of the presentinvention.

BEST MODES FOR CARRYING OUT THE INVENTION

FIGS. 1-3 show a preferred embodiment of the present invention. In thisembodiment, two mosquito coils, each a spiral in shape, are nested onewithin the other.

A radially outward region 11 of each fumigant coil has a steadilydecreasing cross-sectional area, as one moves inwardly from the outwardend of the radially outward region. An ignition region 12 is provided atthe outward end of the radially outward region 11. After lighting theignition region 12 of a fumigant coil, the radially outward region 11burns so as to provide quick coverage of a room or other environmentwith an insect control ingredient such as a repellent. The ignitionregion 12 is adapted to light readily by a reduction of size, theinclusion of conventional oxidants, or the like. Preferably, theignition region 12 is tapered to assist in the ignition of the fumigantcoil.

Inner coil 13 extends unitarily from the innermost end of the radiallyoutward region 11. The inner coil 13 has a substantially uniformcross-sectional area along its length. As inner coil 13 burns itminimizes waste by dispersing a lower, but essentially constant amountof insect control ingredient, when compared to the dispersion rate ofthe burning radially outward region 11. The burn rate of the inner coilis essentially linear. The concentration of the insect controlingredient present in the air of an enclosed area can remain high forextended periods after the initial build-up.

The radially outward region 11 of each coil preferably has two to fivetimes greater cross-sectional area than the steady state cross-sectionalarea of the inner coil 13. The inner coil 13 can terminate in anenlarged area 14 so as to provide support for a conventional coil stand(not shown). Preferably, the various regions of the coil smoothly mergeinto each other, without abrupt changes in size.

The fumigant of FIGS. 1-3 is designed so that the two coil spirals maybe separated from each other prior to use, by pulling them apart. Itshould be understood that portions 11, 12, 13 and 14 may have anycross-sectional geometry, including circular, elliptical, oval,rectangular, triangular, etc., or any combination thereof. It is insteadthe relative size of the cross-sectional areas which is important.

FIG. 4 shows a second version 20 of the present invention that issimilar to the FIG. 1 embodiment except that a third spiral is providedthat is nested within two other spirals.

FIG. 5 shows a third version 30 of the present invention that has just asingle spiral. Note that when manufacturing this coil, a gap is leftbetween each spiral "ring" to prevent the coil from burning straighttowards the center (instead of around the coil).

A related aspect of the present invention is the inclusion of urea inthe composition from which the coil is formed: ##STR1## so that the coilis much more flexible. Surprisingly, the applicants have learned thatthe addition of urea adds sufficient flexibility to the coil to reducethe rate of coil breakage during manufacture, handling, and use, withoutintroducing unacceptable odor or burning characteristics. The urea ispreferably between 0.10% and 5.0% by weight of the composition. Mostpreferably, the urea comprises 0.80% by weight of the composition. Anexample formulation is:

    ______________________________________                                        Material            Wt. %     Wt. % Range                                     ______________________________________                                        Pynamin Forte (allethrin)                                                                         0.22      0.05-2.0                                        Deodorized Kerosene 1.00      0.05-5.0                                        Tabu Powder (Jiket)-Sticky Powder                                                                 4.00      1.00-40.0                                       Starch              20.00     1.00-40.0                                       Wood Powder (sawdust)                                                                             5.00      1.00-50.0                                       Coco Shell Powder   35.00     1.00-50.0                                       Peanut Shell Powder 33.28     0.05-50.0                                       Dye                 0.20      0.001-1.0                                       Perfume             0.30      0.01-5.00                                       Preservative (e.g. potassium sorbate)                                                             0.20      0.01-2.00                                       Urea                0.80      0.10-5.00                                       ______________________________________                                    

Note in particular the use of small amounts of kerosene (preferablydeodorized kerosene) and peanut shell powder. The kerosene overcomesignition difficulties that can be caused by the enlarged radiallyoutward region, and the peanut shell powder, due to its oily contentprovides smoother burning characteristics (notwithstanding the presenceof the kerosene). Interestingly, even with the use of highly flammablekerosene, the coils of the present invention still have acceptably longlife.

The mosquito coils of the present invention are mostly formed from aburnable "base" material. Representative materials used for the base arewood powder (e.g. sawdust), and various vegetable shell powders (e.g.coco shell; peanut shell). However, a wide variety of other slow burningmaterials can also form part of the base (so as to provide a coil whichwill last seven hours or more).

The coils of the present invention repel and/or kill flying insectswhich may be present in living quarters or other selected enclosed oropen spaces. The coils contain an effective amount of an insect controlingredient, preferably uniformly dispersed throughout the base material.Generally, this is from 0.05-3.0% by weight of an insecticidalagent/repellent.

Traditionally, pyrethrum or pyrethroid type materials are useful inmosquito coils. Preferred pyrethroids (from the standpoint of expenseand activity) are pyrethrum, resmethrin, bioallethrin, allethrin, andmixtures thereof. A particularly preferred insecticide is allethrin.Other insect control ingredients can be used such as the repellentscitronella, lemon grass oil, lavender oil, cinnamon oil, neem oil, cloveoil, sandlewood oil, and geraniol, and the insect growth regulatorhydroprene.

The mosquito coils of the present invention may also incorporate variousother burning aids which assist in sustaining the burning of themosquito coil. Traditional and conventional burning aids can beutilized, such as sodium and potassium nitrate, and mixtures thereof.Further, other standard ingredients may be incorporated into themosquito coil, such as dyes, pigments, perfumes, etc.

To manufacture the preferred coil, one can use a variety of techniques.In one preferred method, one first mixes the powders (other than thestarch) with the dye, perfume, and preservative. These materials areblended at room temperature.

A quantity of water having a weight roughly equal to the weight of thefirst blended mixture is then heated. One will want to heat the water toabout 150° F. (about 65.6° C.) for colder water soluble starches and toabout 180° F. to 200° F. (about 82.2° C. to 93.3° C.) for hotter watersoluble starch. All or a portion of the starch is slowly sifted into thewater as it is heated (until the starch thickens). At this point, theurea is added to the starch/water mixture, and the material is mixeduntil uniform.

While one method is to add all of the starch to the heated water,alternatively only a fraction (e.g. 20%) of the starch can be thickenedin this way, with the remainder of the starch being added later with thepowder. Moreover, the amount of water can be varied to be more or lessthan equal to the weight of the non-starch powders plus dye, perfume,and preservatives. Of course, if excess water is added, it will takelonger to later remove the water during the drying step discussed below.

The urea/water/starch mixture is then removed from the heat, and slowlyblended in with the powder mixture to create a dough-like mass. When themixture is essentially uniform, and only slightly warm, the insectcontrol ingredient plus kerosene is blended in until the dough isuniform.

The dough is then preferably extruded into a ribbon sheet and cut intothe desired coils. Alternatively, other techniques can be used to formthe coils from the dough. After the coils are formed, they are thendried by a conventional means, such as forced air drying in a low heatoven.

It should be understood that the exact techniques for creating the coilsare not critical. It is the shape and size of the coils (especially neartheir radial periphery), and the chemical composition of the coils, thatare important for purposes of this patent.

INDUSTRIAL APPLICABILITY

The invention provides mosquito coils and other burnable insect controldelivery devices. Such devices can be placed in a room or other open orclosed environments, lit, and then serve to repel insects.

We claim:
 1. In a burnable insect control ingredient delivery devicecomprising:(a) an insect control ingredient and (b) at least oneburnable base material selected from the group consisting of woodpowders and vegetable shell powders; the improvement characterizedby:the device further comprising (c) 0.1% to 5% by weight urea; andthedevice is a coil.
 2. The burnable insect control ingredient deliverydevice of claim 1, wherein the insect control ingredient is an insectrepellent.
 3. The burnable insect control ingredient delivery device ofclaim 1, further comprising at least 0.05% by weight of kerosene.
 4. Theburnable insect control ingredient delivery device of claim 3, furthercomprising at least 0.05% by weight of peanut shell powder.